DFT study of the ligand effects on the regioselectivity of the insertion reaction of olefins in the complexes [HRh(CO)₂(PR₃)(L)] (R = H, F, Et, Ph, OEt, OPh, and L = propene, styrene)

Abstract

In this work, we have applied Density Functional Theory calculations to investigate the electronic and spacial effects of different phosphorus ligands on the selectivity of the olefin (propene and styrene) insertion reaction into the RhAH bond of the complexes HRh(PR 3 )(CO) 2 (olefin), where the modified ligand PR 3 , is a phosphine (R ¼ H, F, Et, Ph) or phosphite (R ¼ OEt, OPh). M06/SBKJC/cc-pVDZ calculations revealed that the olefin coordination and insertion reaction are dominated by the electronic effects of the phosphorus ligands. A very good correlation between the Tolman electronic factor, v, with the backdonated charges from the metallic center to the olefin and also with the interaction energy of the olefin with the four-coordinated HRh(CO) 2 (PR 3 ) catalyst was found. Using the propene as the substrate and for all the phosphorus ligands investigated, the insertion always proceeds through the reaction path leading to the linear metal-alkyl intermediate. However, when styrene is used, the branched metal-alkyl intermediate is always favored. The structural results obtained for the transition states do not support the existence of a p-allilic intermediates. The regioselectivity obtained for the insertion reaction of styrene results from thermodynamic aspects of the reaction in which the branched metal-alkyl intermediate is always favored by $5 kcal/mol. The M06/SBKJC/cc-pVDZ results are in good agreement with the experimental findings.

Applications and validations of the Minnesota density functionals

“…Dias et al [123] employed M06 to investigate the electronic and spatial effects of different phosphorus ligands on the selectivity of the olefin (propene and styrene) insertion reaction into the RhH bond of the complexes HRh(PR 3 )(CO) 2 (olefin). They found that M06 results are in good agreement with the experimental findings.…”

The fate of branched and linear isomers in the rhodium-catalyzed hydroformylation of 3,4,4-trimethylpent-1-ene

“…homogeneous process catalyzed by transition metal complexes, that is, low valent cobalt or mainly rhodium catalysts [5][6][7], unmodified or modified with phosphine ligands [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Phosphine-modified rhodium catalysts are in general active at high temperature only (T C 100°C), whereas unmodified Rh catalysts work well even at room temperature (rt) or below T & 60°C [23].…”

Rhodium Pyrrolylphosphine Complexes as Highly Active and Selective Catalysts for Propene Hydroformylation: The Effect of Water and Aldehyde on the Reaction Regioselectivity

“…Therefore, extensive research has been devoted to the design of new ligands to enable the selective production of linear aldehydes and then linear alcohols . Theoretical studies on the effect of ligands on the hydroformylation reaction have made important contributions to this field …”

“…Mono‐ and bidentate ligands that contain terminal or internal double bonds and different substituents and functional groups have been applied in the hydroformylation of olefinic substrates. Experimental and theoretical results indicate the advantages of π‐acceptor ligands to facilitate the formation of linear products . In this context, N ‐pyrrolylphosphines should be mentioned.…”

“…[1][2][3][4][5][6][7] Theoretical studies on the effect of ligandsonthe hydroformylation reaction have made important contributions to this field. [8][9][10][11][12][13] The catalytic systemsu sed most frequently for hydroformylation contain Rh I precursors and modifying Pl igands used in excess relative to Rh. Mono-and bidentate ligandsthat contain terminal or internal double bonds and different substituents and functional groups have been applied in the hydroformylation of olefinic substrates.…”